One week after receiving a negative review from Fairfax County planners, developers are hoping revisions will help them win approval tonight of a $400 million project to help turn mostly rural Centreville into one of the county's most intensely developed urban centers.

The project's primary developer, Cadillac-Fairview Co., wants to build a new downtown for Centreville called Trinity Centre, a 125-acre project that would include nine 10-story office buildings, a 300-room hotel, garden apartments, a movie theater and restaurants built around a three-acre lake.

The development, which is scheduled to be considered by the Planning Commission tonight, has gained support from some community activists and county officials who view it as an opportunity to give an identity and focus to a community that frets about being swallowed in the county's fast-paced growth.

"It is going to be and it should be the centerpiece for Centreville," said Planning Commissioner Peter Murphy, whose Springfield District is where the project would lie. "It means a lot to Centreville. That's why we have to be sure of what we're doing."

Despite the planning staff's concerns that more road improvements are needed, a spokesman for Cadillac-Fairview said yesterday that the sticking points would be resolved in time for the public hearing and vote scheduled for tonight.

The meeting begins at 8:15 p.m. in the A level boardroom of the Massey Building, 4100 Chain Bridge Rd.

The Cadillac-Fairview project is one of several developments earmarked for the Centreville area that could generate more than 6,000 residential units and several million square feet of office, retail and hotel space over the next 20 years, planners said.

Much of the development would take place within a prime tract, where Rte. 28, Rte. 29 and I-66 converge in southwestern Fairfax County, an area considered one of Fairfax's hot development sites because of its access to the three major highways and to Dulles International Airport.

Just one-half mile south of the proposed Trinity Centre, another developer, Hazel/Peterson Cos., has plans to build a primarily residential development of more than 3,350 units, including single-family houses, town houses and multifamily units. Centre Ridge will be located between I-66 and Rte. 28 and south of Rte. 29. Hazel/Peterson received zoning approval for the 448 acres last winter, and is set to begin construction of roads within two months, and residential units in the fall.

"I believe Centreville is currently being transformed from an outer suburban area to a real community with a mixture of uses, including employment," said Jeff Saxe, vice president of planning at Hazel/Peterson.

The problems that Cadillac-Fairview found itself up against last week are the same ones being grappled with everywhere in this fast-growing region: how to cope with traffic congestion.

Last week, the county's Office of Comprehensive Planning recommended that the mixed-use development plan be rejected because the developer had not offered enough road improvements to prevent traffic tie-ups, particularly at the intersection of Rtes. 28 and 29.

The developer "has not focused attention on the key improvements needed to make this project work, and therefore has not adequately reduced the impact the project will have on the roads which the applicant intends to use," the planners' report said.

Cadillac-Fairview and the Artery Organization, which is developing residential units in the Trinity Centre project, have offered about $17.5 million in road improvements, including the widening of Rte. 29 to six lanes. This week, in a concessionary move, the developer offered to provide for the design of the interchange at Rtes. 28 and 29, according to Cadillac-Fairview spokeswoman Nancy Card.

Planners in the staff report also were concerned that the project did not offer enough residential units in proportion to the commercial development.

The developers of Trinity Centre want to change the property from a commercial district zoned for a regional shopping center to a planned development commercial district. The Planning Commission, if it votes on the matter tonight, would make a recommendation to the County Board of Supervisors, which would make the final decision.

Commissioner Murphy said yesterday afternoon he had not decided whether to seek a postponement of the matter because of the county planners' negative report on the project.

But a spokesman for Cadillac-Fairview said the problems were being resolved this week after intense negotiations between the county and the developer.

Some community activists are surprised at the planning staff's critical report.

"Trinity Centre has as much to offer as any of the other developments and in some ways more," said Harold Dodson, the Springfield District's representative to the Fairfax County Federation of Civic Associations.

Dodson believes the traffic problems caused by the development would be minimal, because much of the traffic will be flowing into the development, rather than in the opposite direction.

And with the fast-paced development now taking place in his area, Dodson said he considers Trinity Centre "sort of a drop in the bucket."